OBJECTIVES/SPECIFIC AIMS The long term goal of this collaborative research project is to determine whether tumor-specific exosomal proteins may aid in the diagnosis and/or management of patients with breast and colorectal cancer. It is important to emphasize that the study of serum exosomes in health and disease is a nascent field of inquiry and there are many unanswered questions. Although exosomes have been found in the serum of normal individuals and cancer patients, it is unknown whether there are quantitative and/or qualitative differences in the levels and/or the composition of serum exosomes in these two populations. Before embarking on this analysis, it will be important to determine whether there are differences in serum exosomes among normal individuals based on age, sex and race. This is important baseline information. We will then determine if there are differences in serum exosomes between normal individuals and cancer patients. We will compare patients with early stage and advanced cancers, and whether the composition of serum exosomes changes in response to treatment. These preliminary studies will help determine the ultimate role of serum exosomes in the diagnosis and management of patients with breast and colorectal cancer.